Unreal Engine 5.8 Adopts Microsoft Tech To Slay PC Shader Stutter
For those unfamiliar with the concept of shader compilation stutter, it's the hitching that happens when a game loads a new asset or effect for the first time. It's one of the main causes of distracting stuttering in PC games, although it's important to distinguish it from other forms of stutter, like traversal or PSO creation stutter. These can also result in FPS drops, but those aren't as easily solved.
On fixed hardware platforms like consoles, shader compilation stutter is no concern at all because every game can ship with exactly the pre-compiled shaders it needs to run properly on the hardware, as the target platform is fixed, unlike the wildly varying PC platform. Shaders have to be compiled not only for each individual piece of target hardware, but also for the specific driver version in use. For this reason, this approach was previously considered impossible on the PC, but Valve decided to run with it for the Steam Deck, and Microsoft took notice.
Indeed, DirectX ASD was originally introduced for the ASUS ROG Xbox Ally handhelds to provide feature parity with the Steam Deck's Vulkan Shader Pre-Caching. At that time it was only available for specific models of AMD's RDNA-based integrated graphics running specific driver versions. With time, ASD has expanded to desktop GPUs from all three vendors as well as Intel and Qualcomm integrated GPUs on recent-generation hardware.
With that in mind, engine-level support for the feature within Unreal Engine could be a genuine game-changer for developers. By utilizing ASD, Unreal Engine 5.8+ games could both avoid shader compilation stutter and also skip over the lengthy shader pre-compilation phase that's available or mandatory with many modern releases, and sometimes incomplete despite the long compile time required.
Per the official Unreal Engine documentation on DirectX Advanced Shader Delivery, developers are still advised to keep their bundled Precompiled Shader Database (PSO) cache and PSO precaching setup, since ASD is only available for "a limited set of recent drivers." Advanced Shader Delivery is also only available on the Windows and Xbox Stores, although Microsoft has promised that the feature will come to Steam and the Epic Games Store eventually.
